In this retrospective cohort study, Kwok et al investigated survival to discharge status in cases of non-traumatic cardiac arrest where endotracheal intubation (ETI) was attempted by paramedics in a metropolitan emergency medical services (EMS) system in the USA.
The authors retrieved data for all eligible cases between 1 March 2007 and 30 April 2011 from a cardiac arrest database. These cases were then linked to corresponding records from an airway management registry, which are completed by the paramedic responsible for airway management after each resuscitation attempt. Paramedics within this system are authorised to perform ETI during cardiac arrest and to utilise rapid sequence intubation (RSI) using sedation and neuromuscular blockade where required.
A total of 3 284 cases were identified. Cases with a pre-existing endotracheal or tracheostomy tube (n=11), a do-not-attempt-resuscitation order (n=116) or where the airway management approach could not be determined (n=24) were excluded from analysis. The remaining cases were classified as ETI attempted without RSI (n=2 576, 82%), RSI attempted (n=471, 15%), or no ETI attempt (n=86, 3%).
Data were analysed using Fisher's exact test and multivariate logistic regression analysis, controlling for factors known to influence survival such as provision of bystander CPR, response time and presenting rhythm.
Survival to hospital discharge was 11% (n=291) in the ETI without RSI group, 48% (n=226) in the RSI group, and 71% (n=61) in the no ETI group. Overall, 18% of patients survived to hospital discharge, with 41% of patients in the no ETI group achieving return of spontaneous circulation (ROSC) prior to paramedic arrival.
The first pass success rate was higher in the ETI without RSI group compared with the RSI group (72% vs 64%). Overall ETI success rates in the non-RSI and RSI groups were 99% and 98% respectively.
Patients in the ETI without RSI group were most likely to have suffered an unwitnessed arrest and least likely to have presented in a shockable rhythm. In the unadjusted analysis, cases in the RSI group were more likely to survive to discharge than those in the ETI without RSI group (OR 7.2, 95% CI 5.8–9.1). When compared with the ETI without RSI group, cases in the no ETI group were more likely to survive to discharge (OR 2.6, 95% CI 1.6–4.6). These same relationships were observed when more complex multivariate analyses were performed.
In this study, RSI was performed in approximately one in seven cases of cardiac arrest, and was associated with a better prognosis than those undergoing ETI without RSI. Although RSI was used more frequently in patients with favourable characteristics, this relationship persisted when multivariate analysis was performed.
Airway management employing sedation and neuromuscular blockade is generally reserved for cases where airway reflexes are intact, and it may therefore be that the need for RSI in this study is simply a marker for patients with a better prognosis.
The majority of studies relating to paramedic RSI have concentrated on the use of this procedure in the setting of traumatic brain injury. This study provides interesting evidence for the potential role of paramedic RSI in cardiac arrest, which is more frequently encountered in paramedic practice than major trauma.
These results must be interpreted in the context of an EMS system which selectively targets paramedics to calls, is characterised by high standards of training, education and governance, and provides additional training and exposure for paramedics performing less than 12 intubations per year.